The present invention relates generally to hazardous wastes, and, more specifically, to vitrification thereof for long term storage.
The disclosure of U.S. Pat. No. 5,678,237, which provides a method of in-situ vitrification of waste materials in a disposable canister, is hereby incorporated herein by reference. The disposable canister is a module comprising an inner container, an outer container, and insulation therebetween. The outer container serves as the traditional disposal container typically made of steel, which is thermally insulated from an inner container, typically of made of graphite. The inner container serves as a crucible to melt a waste/frit mixture and contain a molten vitrified product. The inner container is typically made of graphite and is typically heated by induction.
The invention, which is the subject of this application, is a means and a method to maximize the delivery of inductive energy to the inner graphite container, minimize heating of the outer container, minimize the thickness of the inner container, and because of the minimization in thickness of the inner container, correspondingly increase the volume inside the canister which is available for waste. The invention relates to the use of a pyrographite layer on the exterior wall of the inner container.
Accordingly, it is desired to provide an Advanced Vitrification System Pyrographite (AVSP) to practice an improved method for modularly processing and vitrifying waste materials, such as nuclear waste, in a disposable canister. A combination, method of using and method of making a pyrographite layer on the exterior wall of the inner container is the innovation sought to be protected.
A device for improving waste vitrification in a disposable canister, the process for using the device, and the process for making the device. The disposable canister, also known as a module, is composed of outer and inner containers with thermal insulation therebetween. The device includes an inner container, typically made of graphite, having a layer of pyrographite on its external wall. The outer container is typically made of stainless steel. The inner container is heated, typically by induction, to melt the frit and waste. The melted mixture is then cooled to form a vitrified product in the module. The fabrication of the pyrographite coating on the inner container involves heating the container to about 1500 degrees centigrade in a methane atmosphere, then cooling the container to ambient temperature.